1. Field of the Invention
The present invention relates to a method for preparing a partial or a full plated denture for the upper and the lower jaws by the direct impression method having improved accuracy within a short period of time in an economical manner, using photo-polymerizable resins.
2. Prior Art
Heretofore, the preparation of plated dentures has relied upon the indirect methods, and has required a number of stages. In the prior art, a great deal of time and labor have been required to obtain finished plated dentures, and specific instruments have been used in the respective steps. For instance, the steps required to prepare plated dentures with the use of thermal-polymerizable resin systems involve a number of processes such as preliminary impression taking; preparation of models; preparation of individual impression trays; trying-in of individual impression trays in the oral mouth; functional impression taking and muscle plasty; preparation of working models; correction of working models; preparation of bite plates; bite taking; attachment of articulators; arrangement of artificial teeth; trying-in and adjustment of wax dentures in the oral mouth; formation of gingival portion; investment of wax dentures; wax washing out; application of resin separators; resin doughing; resin filling; thermal-polymerization of resins; removal of polymerized dentures; and polishing. Thus, it generally takes a period of about four to six weeks for the patient to give access to the finished plated denture, during which a considerable amount of labor and a great number of the instruments used in the respective steps are required.
Attempts have been made to reduce an extended period of time, a great deal of labor and a large number of instruments applied in the respective steps, which are caused by a large number of the steps for preparing plated dentures. Japanese Patent Laid-Open Publication No. 60-90552 teaches among others, use of a photo-polymerizable resin, and Japanese Patent Publication No. 46-24868 as well as U.S. Pat. Nos. 3,460,252 and 3,621,575 teach use of self curing resins. In these specifications, the photo-polymerizable and self curing resins are used in place of the thermal-polymerizable resin to substitute them for wax dentures in the steps of preparing plated dentures of the thermal-polmerizable resin system, whereby it is possible to omit some of the craftsman's procedures such as investment of wax dentures, wax washing out, application of resin separators, resin doughing, resin filling, removal of polymerized dentures, etc.
The method for preparing plated dentures with the use of thermal-polymerizable resin systems involves a great number of steps and requires a considerably prolonged period and a great deal of labor to obtain finished dentures. Further, considerable types of instruments should be used in the respective steps. For that reason, there is inevitably a rise in the price of finished plated dentures. Still further, the finished plated dentures are not always enhanced in the fitting accuracy in the oral mouth. In other words, noticeable difficulty is encountered in obtaining precise working models, since errors occur in the procedures for reproducing the oral mouth conditions thereon such as, for instance, making of individual impression trays, trying-in of individual impression trays in the oral mouth, functional impression taking, muscle plasty, preparation of working models and correction of working models. Still further, the thermal-polymerizable resin in itself has a large shrinkage upon polymerization of as high as about 9.5%, so that there occur errors such as misalignment of the upper and lower halves of the flask in which the resin is filled when it is replaced for wax dentures, unfitness caused by the thickness of flashes, deformation of gypsum at the time of polymerization, deformation of resin due to rapid heating or cooling, deformation of dentures at the time of removing the dentures from the investing stone, etc. This makes it very difficult to obtain plated dentures with improved fitting accuracy.
On the other hand, the method for preparing plated dentures with photo-polymerizable and self curing resins can be carried out in a smaller number of steps as compared with the method in which the thermal-polymerizable resin is used, since the steps of replacing resin for wax dentures can be omitted. However, that method still requires a considerably number of steps and a great deal of time to be consumed by the time the plated dentures are completed, during which a great deal of labor is also needed. In addition, the instruments used in the respective steps are considerably large in type and number. For such reasons as mentioned just above, the price of the finished plated dentures is none too low. In view of the fitting accuracy of the finished plated dentures in the oral mouth, the aforesaid method is still unsatisfactory. In other words, the method for preparing plated dentures with the photo-polymerizable resin and self curing resin still requires the step of reproducing the oral mouth conditions on working models, during which errors are apt to be left as they are. Referring to the photo-polymerizable resin, only one type of a photo-polymerizable resin having a high viscosity should be used, so that difficulty is encountered in obtaining plated dentures with improved fitting accuracy, since the details of the surface of gypsum models are only reproduced with poor fidelity. When the self curing resin is used, curing begins to take place at a very early stage, so that manipulation is very troublesome. It is thus very difficult to obtain plated dentures with satisfactory fitting accuracy.